本論文提出基於Cockcroft-Walton (CW)倍壓電路之柔性切換單相高升壓比交流-直流轉換器，其電路架構由一個升壓電感器、一個雙向開關、一個輔助電路與一個CW倍壓電路所組成。相較於傳統CW倍壓電路，本文提出之轉換器利用功率因數修正技術，使得轉換器達到單位功率因數、低的失真電流與提供一可調的高輸出直流電壓。為了減少開關的切換損失與電磁干擾問題，本文於轉換器中加入一輔助電路，操作在固定切換頻率下，使主開關與輔助開關皆達到零電流切換，文中亦說明提出之轉換器操作原理、電路元件設計考量與控制策略。本文實作輸出功率500瓦特與輸出電壓1200伏特之系統電路，以主動式功率因數修正IC UC3854作為控制核心，最後模擬系統電路與量測實驗結果，驗證提出之轉換器的可行性。

This paper proposes a single-phase soft-switching high step-up ac-dc converter based on Cockcroft-Walton voltage multiplier (CWVM) with power factor correction (PFC), which is formed by one boost inductor, one bidirectional switch, one auxiliary circuit and a CWVM. By applying PFC technology, the proposed converter promises a nearly unity power factor and low distorted line current and provides adjustable high step-up dc voltage that conventional CWVM circuit cannot achieve. In order to reduce the switching losses and EMI, an auxiliary circuit for implementing soft-commutation is added to the power stage of the proposed converter. Operating at fixed switching frequency, in which both main and auxiliary switches are turned off with ZCT. The operation principle, design considerations and control strategy of the proposed converter all are detailed and investigated in this paper. A 1.2kV/500W laboratory prototype, which employs a commercial PFC IC UC3854 as controller, is built for test, measurement and evaluation. Finally, simulation and experimental results demonstrate the validity of the proposed converter.

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